Cores are brought up to the surface within the drill dome, laid out for examination and then cut into segments for storage. From left, expedition leader Ellen Mosley-Thompson, Roberto Filippi and Benjamin Vicencio.

Tough as ice

OSU team drills record core to bedrock despite operational setbacks

From staff reports

Posted May 28, 2010

Researchers at The Ohio State University are hopeful that a new ice core they drilled from a high plateau on the Antarctic Peninsula will contain ice dating back into the last ice age about 12,000 years ago. If so, that record should give new insight into past global climate changes.

The expedition recovered an ice core that was 445.6 meters long, the longest yet recovered from that region of Antarctica.

And while remarkably successful, the fieldwork tested the researchers’ resilience more than most of their previous expeditions.

“It was the field season from hell,” said Ellen Mosley-Thompson, professor of geography at The Ohio State University and leader of the project. “Everything that could go wrong did, and almost everything that could break did.”

Bad weather delayed their transport to the remote drill site and snowstorms were a recurrent problem, preventing support flights from reaching the team. Their drills twice became stuck deep in the ice, a drill motor broke and all three of the drill gearboxes failed, causing them to cannibalize those devices to construct a new one.

Their effort was part of the much larger LARsen Ice Shelf System, Antarctica (LARISSA) project, designed to unravel past climate conditions in that part of the continent and monitor current ocean and atmospheric processes to better understand what likely caused portions of the massive Larsen B Ice Shelf to disintegrate in 2002.

One goal of the LARISSA project is to build a climate history of the region, hopefully determining if the ice shelf break-up was part of a long-term natural cycle or linked to the recent warming in that part of the world.

Photo Courtesy: Ellen Mosley-Thompson, Ohio State University

A Twin Otter delivers supplies and carries away ice cores.

Photo Courtesy: Ellen Mosley-Thompson, Ohio State University

Packaged ice cores stored in a snow pit.

An earlier team of LARISSA researchers had used ground-penetrating radar to map the bedrock under the ice field to identify a suitable drill site. Mosley-Thompson’s six-person team flew by ski-equipped airplane to the Bruce Plateau from the British research station, Rothera, on the west side of the Antarctic Peninsula.

Arriving at the location, the team set up sleeping tents, a cook tent and the large geodesic dome that protected the drilling and core processing operations. The team began drilling on New Year’s Eve, Dec. 31, 2009.

Two days later, the team had drilled 140 meters when the drill became stuck in the ice. Leaving that drill in the ice, they began drilling a second hole, and by Jan. 21, they had retrieved 383 meters of core before that drill also became stuck.

They modified a device normally used to bale water from the drill hole to carry ethylene glycol (antifreeze) down to the top of the stuck drill. After several days, the drill broke free and drilling resumed.

“The guys on our team, Victor Zagorodnov and Vladimir Mikhalenko, engineered through each problem that arose and were really very creative,” explained Mosley-Thompson, who is also director of the university’s Byrd Polar Research Center.

On Jan. 28, the team reached the bedrock at the bottom of the ice sheet. The same day, they recovered the first drill that had become stuck in early January. Both ice cores were cut into roughly one-meter-long segments that were packaged in plastic sleeves and cardboard tubes and stored in a snow pit adjacent to the drilling dome.

Periodically, as weather allowed, a plane would pick up the ice-filled tubes, packed in insulated boxes, and return them to freezers at Rothera. The RVIB Nathaniel B. Palmer, one of two research vessels operated by the U.S. Antarctic Program, retrieved the cores in April. The cores will eventually reach Columbus, Ohio, by refrigerated truck.

When the ice arrives, researchers will begin their analyses, measuring oxygen-isotopic ratios — a proxy for temperature — and concentrations of dust and various chemicals, including volcanic tracers, which collectively will reveal past climate conditions.

They’re hoping for answers to some specific questions:

Do climate trends around the Antarctic Peninsula reflect those experienced by the rest of the continent? Some evidence has suggested conditions have been considerably different.

Was the climate on the peninsula warm during the early Holocene period, some 8,000 to 6,000 years ago, as it was elsewhere around the globe?

Do the cores contain ice formed during the last glacial stage (sometimes referred to as the last ice age)? If so, it might yield clues to what caused the change from those earlier, much colder climate conditions.

“My gut feeling is that the ice at the Bruce Plateau site might have built up during the latter part of the last glacial stage,” Mosley-Thompson said, referring to a time more than 10,000 years ago.

“But to date, only two cores drilled in the Antarctic Peninsula, one in 2007 to 363 meters depth by the British Antarctic Survey, and ours, have the potential to answer that question and neither has been analyzed yet to make that determination,” she added.